1. Field of the Invention
This application is a 371 of PCT/NL03/00750 filed Oct. 31, 2003.
The present invention relates to a method for determining the quality of plant material, such as for instance whole plants, leaf material, fruits, berries, flowers, flower organs, roots, seeds, bulbs, algae, mosses and tubers of plants, by making chlorophyll fluorescence images, particularly a method wherein a characteristic chlorophyll fluorescence image is calculated from the measured chlorophyll fluorescence images and more particularly a method wherein said characteristic fluorescence image contains information about the quantum efficiency of the photosynthetic activity of photosynthetic system of the plant material. The present invention further relates to a device for measuring the chlorophyll fluorescence images and calculating the image of the quantum efficiency of the photosynthetic activity of the photosynthetic system of the plant material from said chlorophyll fluorescence images. The present invention also relates to a device for sorting and classifying plant material on the basis of the chlorophyll fluorescence images and the image of the quantum efficiency of the photosynthetic activity of the photosynthetic system of the plant material calculated from said chlorophyll fluorescence images.
2. Description of the Related Art
The common method of measuring the quantum efficiency of the photosynthetic activity of plant material, is measuring the photosynthetic activity using U. Schreiber's pulse amplitude modulation (PAM) fluorometer described in “Detection of rapid induction kinetics with a new type of high frequency modulated chlorophyll fluorometer” Photosynthesis Research (1986) 9: 261-272. In this method the quantum efficiency of the photosynthetic activity is determined. To that end first the fluorescence yield, FO, is measured in the dark or at a low light intensity of the ambient light. Then the maximum fluorescence yield, Fm, is determined at a saturating light pulse. From the two measuring signals the efficiency of the photosynthetic system can be calculated according to Q=(Fm−FO)/Fm. Said measuring method determines the efficiency of the photosynthetic system of a small surface of a leaf, a so-called spot measurement and therefore is not imaging.
Known measuring methods that are imaging, work according to the same principle as the PAM fluorometer. A known measuring method is the one of B. Genty and S. Meyer, described in “Quantitative mapping of leaf photosynthesis using chlorophyll fluorescence imaging” Australian Journal of Plant Physiology (1995) 22: 277-284. In this method the surface of the plant material, for instance a leaf, is irradiated in short pulses with electromagnetic radiation from a lamp and the fluorescence is measured during the pulses with a camera system. Said first measurement takes place in the dark or at a low light intensity and results in the FO measurement. The next measurement is carried out at a saturating light pulse and results in the Fm measurement. From said measurements an image can be calculated of the efficiency of the photosynthetic system. A drawback of this method is that a large surface of for instance 50×50 cm2 cannot be irradiated with a saturating light pulse. The present light sources are not bright enough to irradiate such a surface with sufficient light intensity.